The radiator is the single most important component in your vehicle's cooling system. Comprised of many narrow metallic tubes, it allows for the expulsion of heat through the front of your vehicle. Hot coolant flows from the engine to the radiator, at which point a fan cools off the coolant before sending it back into the engine. If your radiator has a leak, though, it won't be able to keep your engine cool. So, how do you know if your radiator is leaking?
#1) Low Coolant
One telltale sign of a radiator leak is low coolant. When your engine is cold, open the radiator cap to see if any coolant is missing. In most vehicles, coolant should be filled all the way to the neck of the radiator. If your radiator contains less than this, coolant might be escaping through a leak.
#2) Engine Overheating
Of course, a leaking radiator can lead to an overheated engine when neglected. As coolant leaks out, there's less liquid to absorb heat from the engine and release it through the front of your vehicle. Air doesn't transfer heat as effectively as liquid. So, when your radiator leaks, it will likely cause your engine temperatures to rise, eventually resulting in overheating.
#3) Sweet Smell Inside Cabin
You may also discover a sweet smell inside the cabin of your vehicle if the radiator is leaking. Standard 50-50 coolant (antifreeze and distilled water) has a sweet smell. In a vehicle with a healthy cooling system, you won't be able to smell the coolant. But if your radiator is leaking, the sweet-smelling coolant may leak into your engine bay or behind the dashboard.
#4) Coolant Puddle Underneath Car
If you see a puddle of coolant underneath your car, there's a good chance that the radiator is leaking. Radiator leaks are typically small, creating a small puddle that often goes unnoticed to unsuspecting drivers. Before driving in your car in the morning, look underneath it to see if there's a puddle.
#5) Cooling System Not Pressurized
A fifth sign of a leaking radiator is a cooling system that's not pressurized. Cooling systems operate in a pressurized state, so lack of pressure means that some component of your vehicle's cooling system, such as the radiator, has been breached. To see if your cooling system is pressurized, use a pressure testing tool. You hook it up to your car's radiator and pump it full of air to create the desired pressure.